Enhanced topological superconductivity in spatially modulated planar Josephson junctions

TL;DR

This paper introduces a modulated planar Josephson junction device that significantly enhances topological superconductivity and Majorana zero modes by creating minibands with improved properties, broadening operational regimes.

Contribution

It demonstrates that periodic modulation of the junction width enhances the topological gap and robustness of Majorana modes, enabling better control and larger parameter space coverage.

Findings

Enhanced topological gap due to miniband formation

Supports topological phase at low Zeeman fields

Device tunable via gate voltages

Abstract

We propose a semiconductor-superconductor hybrid device for realizing topological superconductivity and Majorana zero modes consisting of a planar Josephson junction structure with periodically modulated junction width. By performing a numerical analysis of the effective model describing the low-energy physics of the hybrid structure, we demonstrate that the modulation of the junction width results in a substantial enhancement of the topological gap and, consequently, of the robustness of the topological superconducting phase and associated Majorana zero modes. This enhancement is due to the formation of minibands with strongly renormalized effective parameters, including stronger spin-orbit coupling, generated by the effective periodic potential induced by the modulated structure. In addition to a larger topological gap, the proposed device supports a topological superconducting phase that covers a significant fraction of the parameter space, including the low Zeeman field regime, in the absence of a superconducting phase difference across the junction. Furthermore, the optimal regime for operating the device can be conveniently accessed by tuning the potential in the junction region using, for example, a top gate.